 /*******************************************************************************
  * Copyright (c) 2000, 2006 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.core.internal.registry;

 import java.lang.ref.SoftReference ;
 import org.eclipse.core.runtime.IContributor;

 /**
  * An object which represents the user-defined extension in a plug-in manifest.
  */
 public class Extension extends RegistryObject {
     public static final Extension[] EMPTY_ARRAY = new Extension[0];

     //Extension simple identifier
 private String simpleId;
     //The namespace for the extension.
 private String namespaceIdentifier;

     // Place holder for the label and the extension point. It contains either a String[] or a SoftReference to a String[].
 //The array layout is [label, extension point name]
 private Object extraInformation;
     private static final byte LABEL = 0; //The human readable name of the extension
 private static final byte XPT_NAME = 1; // The fully qualified name of the extension point to which this extension is attached to
 private static final byte CONTRIBUTOR_ID = 2; // ID of the actual contributor of this extension
 private static final int EXTRA_SIZE = 3;

     protected Extension(ExtensionRegistry registry, boolean persist) {
         super(registry, persist);
     }

     protected Extension(int self, String simpleId, String namespace, int[] children, int extraData, ExtensionRegistry registry, boolean persist) {
         super(registry, persist);

         setObjectId(self);
         this.simpleId = simpleId;
         setRawChildren(children);
         setExtraDataOffset(extraData);
         this.namespaceIdentifier = namespace;
     }

     protected String getExtensionPointIdentifier() {
         return getExtraData()[XPT_NAME];
     }

     protected String getSimpleIdentifier() {
         return simpleId;
     }

     protected String getUniqueIdentifier() {
         return simpleId == null ? null : this.getNamespaceIdentifier() + '.' + simpleId;
     }

     void setExtensionPointIdentifier(String value) {
         ensureExtraInformationType();
         ((String []) extraInformation)[XPT_NAME] = value;
     }

     void setSimpleIdentifier(String value) {
         simpleId = value;
     }

     private String [] getExtraData() {
         //The extension has been created by parsing, or does not have any extra data
 if (noExtraData()) {
             if (extraInformation != null)
                 return (String []) extraInformation;
             return null;
         }

         //The extension has been loaded from the cache.
 String [] result = null;
         if (extraInformation == null || (result = ((extraInformation instanceof SoftReference ) ? (String []) ((SoftReference ) extraInformation).get() : (String []) extraInformation)) == null) {
             result = registry.getTableReader().loadExtensionExtraData(getExtraDataOffset());
             extraInformation = new SoftReference (result);
         }
         return result;
     }

     String getLabel() {
         String s = getExtraData()[LABEL];
         if (s == null)
             return ""; //$NON-NLS-1$
 return s;
     }

     void setLabel(String value) {
         ensureExtraInformationType();
         ((String []) extraInformation)[LABEL] = value;
     }

     String getContributorId() {
         String s = getExtraData()[CONTRIBUTOR_ID];
         if (s == null)
             return ""; //$NON-NLS-1$
 return s;
     }

     public IContributor getContributor() {
         return registry.getObjectManager().getContributor(getContributorId());
     }

     void setContributorId(String value) {
         ensureExtraInformationType();
         ((String []) extraInformation)[CONTRIBUTOR_ID] = value;
     }

     public String getNamespaceIdentifier() {
         return namespaceIdentifier;
     }

     void setNamespaceIdentifier(String value) {
         namespaceIdentifier = value;
     }

     public String toString() {
         return getUniqueIdentifier() + " -> " + getExtensionPointIdentifier(); //$NON-NLS-1$
 }

     /**
      * At the end of this method, extra information will be a string[]
      */
     private void ensureExtraInformationType() {
         if (extraInformation instanceof SoftReference ) {
             extraInformation = ((SoftReference ) extraInformation).get();
         }
         if (extraInformation == null) {
             extraInformation = new String [EXTRA_SIZE];
         }
     }
 }

